This invention relates to a method of producing a spinning solution for producing a polymer fiber, in particular an aramid fiber, which method comprises admixing the polymer with a solvent, and melting, homogenizing, devolatilizing and then discharging the mixture and also to apparatus therefor.
Manufactured polymer fibers are currently needed for many applications in the private and industrial spheres. This applies, for example, to all kinds of garments, reinforcing fabrics, industrial textiles, wear pads, filters, etc. For this purpose, the polymer in question, which is usually present in piece or powder form, is admixed with a solvent, melted, homogenized, devolatilized and then fed while still in the viscous state or remelted after intervening transportation to dies from which it is then extruded under high pressure to form the fiber.
U.S. Pat. No. 5,882,563, for example, discloses a process for making fibers from poly(p-phenyleneterephthalamide) in which sulfuric acid cooled to below its coagulation point is mixed in the form of ice with p-aramid to obtain a solid mixture. Thereafter, this solid mixture is reheated and melted and this liquid is spun through spinning orifices under pressure. The heating of this solid mixture is carried out in two separate zones, namely a melting zone and a pressure build-up zone, with the polymer being kneaded and mixed in the melting zone at least.
The object of the present invention is providing a method and apparatus of the abovementioned type which provides the product with a long residence time while at the same time increasing the shear rates in the apparatus and providing a maximum of flexibility, processing consistency and reduced apparatus components.